drm/mode: introduce wrapper to read framebuffer refcount.

Avoids drivers knowing where the kref is stored.

[airlied: add kerneldoc]
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/msm/msm_fb.c b/drivers/gpu/drm/msm/msm_fb.c
index a474d6c..17e0c9e 100644
--- a/drivers/gpu/drm/msm/msm_fb.c
+++ b/drivers/gpu/drm/msm/msm_fb.c
@@ -77,7 +77,7 @@
 
 	seq_printf(m, "fb: %dx%d@%4.4s (%2d, ID:%d)\n",
 			fb->width, fb->height, (char *)&fb->pixel_format,
-			fb->refcount.refcount.counter, fb->base.id);
+			drm_framebuffer_read_refcount(fb), fb->base.id);
 
 	for (i = 0; i < n; i++) {
 		seq_printf(m, "   %d: offset=%d pitch=%d, obj: ",